Before we start comparing offset printing versus digital printing, let’s first define what each of them are.
Offset printing, also called lithography, uses plates (typically aluminum) to transfer ink to rubber blankets, which then transfer the ink to the paper. Since the ink isn’t directly transferred to the paper, it is called offset.
A full color print job typically only consists of four ink colors: Cyan, Magenta, Yellow, and Black (or CMYK). Each color is applied to a different metal plate. Each plate contains areas that are receptive to grease and areas that are receptive to water. These areas are created by a chemical process – in which the ink sticks to the areas that are receptive to grease; while the areas receptive to water repel the ink. After ink is applied to each plate, the image of ink is then transferred from each plate onto a rubber blanket. Then the rubber blanket transfers the inked image onto the paper. The printed image is a combination of all four inks printed on top of each other from different rubber blankets.
If a specific color in the Pantone Matching System (PMS) is needed, the four color printing process cannot guarantee it will print an exact color match. The only way to guarantee complete accuracy is to print a “spot color”. The ink for this spot color needs to be custom made and applied as a fifth color, requiring its own plate (and blanket).
Digital printing is what it sounds like. Images are digitized through a computer, which then electronically transfers them to paper using a four color (CMYK) process. Similar to offset presses, digital presses cannot guarantee an exact color match. Thus, if an exact color match is needed, a spot color will need to be added to the press as a fifth color.
Time & Money
Because offset printing requires the making of plates, the cost to set up the print run is often pricey. However, once the offset press is set up to accurately print, the printing moves quickly – more so than a digital press. Thus, large print runs can actually take less time to print on an offset press than on a digital press. As a result, it is more cost- effective to large print runs on offset presses than on digital presses.
Since digital presses don’t require a lengthy setup time – such as the time involved in setting up plates for offset presses – digital printing takes less time to print smaller runs. Thus, it is more cost-effective to print small runs on digital presses than on offset presses.
Since digital printing involves transferring ink directly to the paper, the image outlines tend to be slightly blurred and less sharply defined than images printed by offset presses. Thus, offset presses tend to print higher quality products than digital presses.
1050mm x 780mm is the maximum sheet size that can be printed by an offset press. The maximum sheet size for a digital press is 660mm x 356mm. However, large format digital printers can print rolls of paper up to 1625mm wide. The press sheet length on a large format digital printer is only limited to the length of the roll of paper.
Since digital presses don’t require the plates that offset presses require, there’s less waste involved with digital printing. Thus, digital printing is more environmental friendly.